The invention relates to a static dewatering element for a web forming machine, said dewatering element comprising a thermally sprayed coating manufactured of powder particles. The invention also relates to a method for covering a dewatering element designed for a web forming machine.
Dewatering elements of a web forming machine are traditionally manufactured of a solid ceramic material. However, the manufacture of solid ceramic dewatering elements is expensive. Therefore, the dewatering elements can be manufactured at lower cost by covering a suitable metal. Patent FI 96437 proposes a dewatering element consisting mainly of an aluminum profile. The aluminum profile is covered with an oxide layer provided by electrolytic plasma oxidation or spray explosion covering, for example. However, the method according to this patent as well as other known methods can only be used for manufacturing coatings with a porosity of over 1%. Such a high porosity creates a risk of pit corrosion at the boundary of the frame layer and the coating, which can lead to the detachment of the coating during use. In addition, filler particles attach to a porous material, which then consume the fabric contacting the dewatering element. The surface roughness of the dewatering elements according to prior art has typically ranged between 0.4-0.8 μm. The surface roughness is high with known coatings causing fast fabric wear.